This invention relates to a transistorized constant voltage circuit. A constant voltage circuit according to this invention is specifically useful for a load comprising at least one insulated gate field effect transistor (herein called an IGFET) and no other active circuit element or elements.
An IGFET is used either in a logic circuit, for example, a NAND or a NOR circuit, or in a memory circuit as an element of a large-scale integrated circuit (an LSI). For such a circuit, a high power supply voltage level results in a decrease in a speed of operation and an increase in power consumption. A low supply voltage level gives rise to an operation error. Particularly when MOSFET's of a short channel length are used as the IGFET's in the logic and/or memory circuits to provide an integrated circuit with a small-area semiconductor chip, a minimum allowable voltage should be used in order to avoid punch through of the MOSFET's. In any event, an excellent constant voltage circuit is indispensable for such a logic and/or memory circuit. It is also necessary that a constant voltage circuit provide a stable output voltage against fluctuations in the power supply voltage and the load. Preferably, the constant voltage circuit should be readily manufactured as an LSI together with the logic and/or memory circuits. These necessities and requirements are applicable also to a transistorized constant voltage circuit for a more general load.